Telegraph system



June 2, 1931. I G. J. KNANDEL 9 V TELEGRAPH sY s'rEu Filed NOV. 9, 1929 ATTORNEY Patented June 2, 1931 UNITED SATES PATENT OFFICE GEORGE J. KNANDEL, 0F NEWARK, NEW JERSEY, ASSIGN OR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK TELEGRAPH SYSTEM Application filed November 9, 1929. Serial No. 406,071.

This invention relates to telegraph systems and particularly to printing telegraph systems in which the power for driving the printing equipment is controlled from a dis- 5 tant point.

The objects of the invention are to reduce the current consumption and maintenance expenses incurred in the operation of these systems and to render the equipment automatically effective whenrequired for use and to disable it when its service is no longer needed.

It has been proposed heretofore to so arrange a printing telegraph system comprising a number of stations interconnected by a single metallic signal conductor that a call ing station, by applying current to said concluctor, causes the printer drivingmotors at the called stations to start running and continue in operation during signaling. l/Vhen the message has been sent, the distant driving motors may be stopped by disconnecting the source of current at the calling station. In systems of the character above noted, it is necessary, where polarized printer line relays are used, to ground opposite poles of the current sources at any two stations to insure that current flows in the proper direction through the polarized line relays.

According to the present invention, this objection is overcome by so arranging the circuits at each station that like poles of the current sources may be grounded while at the same time current is caused to flow through the line relays in the proper direction regardless of which station initiates the call. This invention is illustrated in the accompanying drawing in which two printer telegraph stations A and B have been shown connected by a single conductor L. At these stations well-known printing apparatus are shown in diagrammatic form in dotted line enclosures 1 andv 2 at stations A and B respectively. The motor-generator mechanisms for driving these printers are also shown in diagrammatic form at 4 and-5 for stations A and B respectively. The line L is normally connected through these printers and their respective printer contacts and operating relays to ground; at station A through contacts of the transfer relay 10 and the winding of line relay 11 to ground and at station B through contacts of the transfer relay 12 and the winding of line relay 13 to ground.

Referring now to the operation of the system, the motor generator at either station may be started and stopped through opera tions performed at the other station. example, if the operator at station A desires to communicate with station B, the motorgenerator at station B would be automatically started as follows: The first operation on the part of the operator A is to close the switch 15 and thus cause a circuit to be completed for the operation of transfer relay 10 from battery, switch 15, winding of relay 10, upper armature and back contact of relay 16 to ground. The transfer relay 10 in op erating closes an obvious circuit for the printer control relay 17 which in turn closes a circuit for starting the motor-generator at 4 from a current supply not shown, but connectilole at point 18. The operation of relay 17 also causes current from the supply connected at 18 to be applied to the printer motor for the starting of the printer 1. Only the conductors for this motor have been shownat 36. Transfer relay 10 also closes a circuit to supply current from the generator at 4 to line L over a circuit as follows: generator at 4, upper inner armature and front contact of transfer relay 10, the printer operating mechanism indicated by the numeral 20 and the break key 21 through the lower armature and front contact of relay 10 to line L. Current is now also provided from the generator at 4 through conductors 22 for the magnets of the printer 1.

Current from the generator at 4 as now supplied over line L causes the operation of the line relay 13 at station B over a'cirouit as follows: from lineL, upper inner armature and back contact of transfer relay 12, through the printer operating mechanism indicated by the numeral 23 and the break key 24, lower armature and back contact of relay 12, winding of line relay 13 to ground. Relay 13 in operating closes an obvious circuit for the slow-to-release relay 26, which in For r turn closes an obvious circuit for the call signal apparatus 27 to call the operator at station B. Relay 26 also closes an obvious circuit for the operation of the control relay 28 which in turn closes a circuit from a current supply not shown but connectible at point 30 for the starting of the motor generator at 5 and for starting the printer motor over conductors 37. lVhen the motor generator is in operation the current for the magnets of the printer at 2 is supplied over conductors marked 31. The operator at B answering the call may, by operating key 33, cause relay 34 to operate and lock and thereby disable the call signal apparatus 27.

The message impulses may now be transmitted over line L by the usual operation of the sending mechanism at 1 and received by the printer at 2 in the usual manner. Due to the slow releasing characteristics of relay 26, this relay will remain operated during the sending of the message even though line relay 13 may follow the impulses.

In case it is desirable not to rely entirely on the slow releasing characteristics 26 to maintain the printer-at 2 in operation during a long open period or so-called break signal a high resistance such as 38 may be inserted across the break key 21 so that when this key is operated some current will still flow in the line. This current is suli'icient to keep the line relay 13 operated during the break signal so that the motor-generator at station B may be maintained in operation. Resistance 38 should therefore be low enough to permit line relay 13 to remain operated when the break key is operated but still sufficiently high so that the polarized printer operating relay will release under these circumstances and thus indicate to the operator that sending of the message has been interrupted. On the other hand to stop the motor-generator at station E all that has to be done is to open the line L for a sufliciently long period to permit relays 13 and 26 to release, which takes place when the switch 15 is opened.

When the message is completed, restoring of the switch 15 at station A. releases transfer relay 10 and the printer control relay 17 and thereby causes the motor-generator at 4 and the printer motor to stop. The stopping of the motor generator at l removes current from line L, and the circuits at station B are also restored to normal by the release of relays 13, 26, 34 and 28; the last mentioned relay stops the motor-generator at 5 and the printer motor.

It should be noted that when the slow-torelease relay 26 was operated, the circuit for transfer relay 12 was opened at the upper armature and back contact so that in case the switch 35 at this station is operated in error during the transmission of a message from station A, transfer relay 12 will not be operated to disturb the established connection. Neither is it possible to apply opposite potential at both ends of the line simultaneously. If the switches 15 and 35 should be closed simultaneously both the transfer relays 10 and 12 may operate. In this case potential would be applied to each end of the line and double current flow if the opposite poles of the generators at both ends of the line were grounded. This will not occur in this system as like poles of the two generators are grounded. If both keys 15 and 35 happen to be operated at the same time the same polarity will be applied to the line at each end and consequently no current would flow in the line. This will be noted by the operators since the printers would not operate. The switch at one station could then be opened in order to cause the system to function.

As the same polarity is grounded at the ends of the line, current may flow in one direction or the other depending on the station initiating the call. However, the operation of the transfer relay at the calling station connects the printer mechanism so that the polar relays therein are provided with the proper polarity of current. It should be noted that normally current will flow from the line through the printer at station A from upper inner armature and back contact of relay 10, and when current is transmitted to the line from station A, the direction of the current through the printer will be in the same direction, i. e., from the upper inner armature and front contact of relay 10.

It should be understood that this disclosure should merely be considered as illustrative of the invention and that the invention may readily be applied in many other systems without departing from the spirit thereof.

What is claimed is:

1. In a telegraph system, two stations, a line connecting said stations, a signaling current source at each station having like poles connected to ground, a transmitting and receiving device at each station, means responsive to signal transmission from one station for conditioning the receiver at the other station for reception of said signals, means for conditioning the receiver at the call originating station for reception of said signals, and means for causing the current of said transmitted signals to flow through the receivers at both stations in the same direction regardless of which station is the call originating station.

2. In a telegraph system, two stations, a conductor connecting said stations, a signaling current source at each station having like poles connected to ground, a signal current transmitter at each station, a signal current receiver at each station, means responsive to impulses of signaling current over said conductor from the transmitter at one station for conditioning the receiver at the other station for reception of said signals, means for causing the signals to pass through the receiver at the call originating station, and means for causing the signaling current to flow in the same direction through the two receivers regardless of which station is the call originating station.

3. In a telegraph system, two stations interconnected by a single metallic signal eonductor, a receiver and a driving motor therefor at each station, means at each station for sending telegraph signals over said conductor to operate the receiver at the distant station, a source of current at each station normally disconnected from said conductor, said sources having like poles connected to ground, means at each of said stations for starting and maintaining the local motor in operation during the sending of message signals and for connecting the free pole of the source thereat to said conductor when calling, means at the called station responsive to the flow of current in said conductor for starting and maintaining the motor in operation during the sending of message signals, said last means serving to stop the operation of the motor when current ceases to flow in said conductor for a definite interval, and means for causing the flow of current in the same direction through the receiver of either station whether it is calling or being called.

4. In a telegraph system, two stations, a conductor connecting said stations, a transmitting and receiving device at each station, a signaling current source at each station normally disconnected from said line, means at the calling station for connecting its source to said line, means responsive to signal transmission from one station for conditioning the receiver at the other station for reception of said signals, means for conditioning the receiver at the call originating station for reception of said signals, and means for causing the current of said transmitted signal to flow through the receivers at both stations in the same direction regardless of which station is the call originating station.

In testimony whereof, I have signed my name to this specification this 8th day of November, 1929.

GEORGE J. KNANDEL. 

